The present invention relates to an electric switch with biased contact spring, said spring comprising two lamellar outer branches and two lamellar inner branches arranged between said outer branches, one of the ends of each of the inner branches being connected by means of a curved part to one end of the near outer branch, the two other ends of the outer branches being connected to each other by means of a transverse connecting part, the free ends of the inner branches being connected to a biasing member arranged for spreading apart said ends from their unstressed position, the biasing member being arranged in fixed relationship with an actuating member and the biased spring co-operating with two fixed stops arranged on either side of the transverse connecting part of the spring. Such a spring is known from the U.S. Pat. No. 4,032,734 according to which the biased spring bears, in a first end position, against a first pointed fixed stop. In a second end position, the biased spring comes into contact with a second pointed stop, arranged approximately symmetrically to the first one, with respect to the longitudinal axis of the spring. Between these two end positions, the spring effects a flexing and a twisting movement about an axis parallel to said longitudinal axis, and the actual snapping movement only takes place over a very small distance.
The structure and the mode of operation proposed in the before-mentioned U.S. patent require relatively large minimum dimensions of the switch so that the stroke of the spring, as well as the actuating force, will be relatively larger than that required by certain applications.
This invention has for its object the provision of a switch which can be of very small dimensions, while having relatively great actuating force and stroke of the contact spring, and yet having a response which is extremely reliable. It is a further object of the present invention to provide a switch which is activated by a very sudden motion of the contact spring, establishing an excellent electrical contact.
This is obtained in accordance with the invention by the fact that each of the two fixed stops which precludes travel of the biased contact spring has a planar contact surface extending at least over the length of the transverse connecting part of that biased contact spring.
Preferably, at least one of the two fixed stops extends over at least one part of the length of the two outer branches of the biased spring.
According to an embodiment of the invention, the actuating member is coupled with a substantially planar return spring, comprising outer and inner substantially annular parts, which are co-axial and connected to each other over a portion of their periphery, the outer part being connected, over a portion of its periphery diametrically opposite to the portion by which it is connected to the inner part, to a part of the return spring which is in fixed relationship with said fixed stops.